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Manheim, Pennsylvania (CNN)Donald Trump on Saturday evening offered up the surest sign yet that he is returning to the bombastic, bare-knuckle style that defined his primary run as he wrapped up a week that raised fresh concerns about his presidential campaign's viability.

Straying from the prepared remarks on his teleprompter, the Republican nominee reignited his attacks on Hillary Clinton's physical and mental health, arguing that the former secretary of state "could be crazy" and lacks the "stamina" to be president -- even imitating Clinton stumbling into her car while leaving a 9/11 ceremony last month.

And just as he is once again drawing attention to former President Bill Clinton's sex scandals, Trump took his political attacks a step further, questioning, with no evidence, whether the Democratic nominee is "loyal" to her husband. The attacks came as The New York Times raised fresh questions about his payment of taxes and business success.

Trump's personally charged rhetoric comes as he continues to defend his performance at the first presidential debate last Monday and as he is working to swat away renewed Republican distress over his candidacy after he doubled down on the latest controversy, drawing attention away from his core campaign message.

"She's got bad temperament. She could be crazy. She could actually be crazy," Trump said, turning away from his teleprompters.

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That's a revival of the line of attack Trump employed nearly two months ago, when he blasted Clinton as "unbalanced" and "totally unhinged," suggesting she "took a short-circuit in the brain."

"Honestly, I don't think she's all there," he said during an August 6 rally.

Those remarks came before he shook up his campaign leadership and reshaped his campaign into one pockmarked by fewer controversies and a heavier focus on policy.

But Trump trained his focus Saturday night not on the issues that have lifted his candidacy, but instead on leveling a series of nasty political attacks on his rival.

"I don't even think she's loyal to Bill, if you want to know the truth. And really folks, really, why should she be?" Trump said, apparently calling into question Clinton's marital fidelity to her husband in his most direct terms yet.

And as he slammed her for her work as secretary of state and pointed to the slew of problems confronting the United States around the world, Trump also raised an incident weeks ago when Clinton stumbled and needed Secret Service agents to hoist her into her van as she left a 9/11 memorial ceremony.

"She's supposed to fight all of these different things and she can't make it 15 feet to her car? give me a break. give me a break," he said. "Give me a break! She's home resting right now. She's getting ready for her next speech which is going to be about 2 or 3 minutes."

Trump then began to stagger on stage, imitating the medical incident Clinton faced when leaving the 9/11 ceremony.

Clinton's doctor revealed later that day that Clinton had just been diagnosed with pneumonia and "overheated" at the ceremony.

And while Trump has largely resisted overtly attacking Clinton over the incident or raising questions about her health, he has lately begun pumping up that line of attack.

Trump delivered his fiery speech before a large crowd of several thousand that waited more than 90 minutes past the rally's slated start time -- and Trump served up his most original, bombastic self that voters got to know best during the Republican primaries.

The punches continued to roll as Trump delved further into his speech -- and most appeared to come as tangents to his prepared remarks.

"She's an incompetent woman," he said.

"She's never done anything meaningful. Never. Her only legacy is death, tremendous financial loss and failure," he added later.